Many vehicles generally have a prime mover or internal combustion engine, a transmission to transmit drive power to move the vehicle, and a mechanism to selectively transfer rotational torque from the prime mover to the transmission. In some approaches, the mechanism to selectively transfer rotation from the prime mover to the transmission includes a manual clutch. A manual clutch is efficient. However, operation of the manual clutch requires extra effort and added operational oversight by the vehicle operator. Such extra effort and added operational oversight can be less desirable, for example it can reduce the operator's efficiency. An alternative mechanism to transfer rotational torque from the prime mover to the transmission is a torque converter.
A torque converter is generally a hydrodynamic fluid coupling that typically transfers the rotational torque from a prime mover to a driven load such as a transmission. The torque converter typically includes an impeller, a turbine, and a stator. The torque converter multiplies the torque from the prime mover and transfers the torque to the transmission. Japanese patent publication JP 2010/169151 to Nissan dated Aug. 5, 2010 discloses a torque converter for an automatic transmission capable of achieving fuel economy and power performance in a vehicle by using a desirable engine rotation profile. The torque converter for the automatic transmission determines a target value expressed by a ratio Ns/Ne. The ratio is based on a rotation speed Ns of a stator and a rotation speed Ne of an engine output shaft based on an operational state of the vehicle, and controls a braking torque with respect to the stator based on the target value. However, the operation of such torque converters can result in lower performance. For example, the operation of such torque converters can result in decreased efficiency and increased operating temperatures.
Accordingly, a torque converter having improved performance is needed.